Air conditioner and method of controlling an air conditioner

Abstract

An air conditioner and a method of controlling an air conditioner are provided. The method of controlling an air conditioner may include determining whether a low-load condition is satisfied on the basis of a number of indoor devices or a temperature of external air, performing a low-load operation of a compressor at a predetermined frequency when the low-load condition is satisfied, detecting whether an operation pressure is out of a target pressure value or range while the low-load operation is performed, and bypassing a refrigerant from the compressor to a gas/liquid separator via an injection passage when the operation pressure is out of the target pressure value or range.

What is claimed is: 
     
       1. A method of controlling an air conditioner including a tank having a gas/liquid separator, a receiver, and a divider to separate the gas/liquid separator from the receiver; an outlet tube that extends from the receiver to the gas/liquid separator; having a bypass passage connected to the gas/liquid separator; a first branch from which an injection passage and the bypass passage are branched; a bypass valve provided in the bypass passage to adjust a flow rate of a refrigerant; an injection valve provided in the injection passage to adjust the flow rate of the refrigerant; a high-pressure sensor that detects a refrigerant discharge pressure of a compressor; and a low-pressure sensor that detects a refrigerant suction pressure of the compressor, the method comprising:
 determining whether a low-load condition is satisfied based on a number of indoor devices or a temperature of external air; 
 firstly performing a low-load operation of the compressor at a predetermined frequency when the low-load condition is satisfied; 
 detecting whether an operation pressure is out of a target pressure range while the low-load operation is performed; and 
 secondly bypassing the refrigerant from the compressor to the gas/liquid separator via the injection passage by opening both the bypass valve and the injection valve when the operation pressure is out of the target pressure range, wherein the low-load condition is satisfied when the number of indoor devices is less than a predetermined number or the temperature of external air is below a predetermined temperature, wherein the bypassing the refrigerant includes:
 when the air conditioner performs a heating operation, changing an opening degree of the injection valve in a state in which the injection valve opens until a pressure detected by the high-pressure sensor is within a first target pressure range, and 
 when the air conditioner performs a cooling operation, changing the opening degree of the injection valve in a state in which the injection valve opens until a pressure detected by the low-pressure sensor is within a second target pressure range. 
 
 
     
     
       2. The method according to  claim 1 , wherein the bypassing of the refrigerant includes introducing the refrigerant into the gas/liquid separator by successively passing the refrigerant through the injection passage and the bypass passage. 
     
     
       3. The method according to  claim 1 , wherein the air conditioner further includes first and second branch tubes branched from a second branch of the injection passage, and wherein the first branch tube extends to a first compressor, and the second branch tube extends to a second compressor. 
     
     
       4. The method according to  claim 1 , wherein, in the heating operation, when the pressure detected by the high-pressure sensor is within the first target pressure range, the bypass valve is closed. 
     
     
       5. The method according to  claim 4 , wherein, in the heating operation, when the operation pressure is out of the first target pressure range, a fuzzy-control of the compressor is stopped, and when the pressure detected by the high-pressure sensor is within the first target pressure range, a fuzzy-control of the compressor is performed. 
     
     
       6. The method according to  claim 1 , wherein, in the cooling operation, when the pressure detected by the low-pressure sensor is within the second target pressure range, the bypass valve is closed. 
     
     
       7. The method according to  claim 6 , wherein, in the cooling operation, when the operation pressure is out of the second target pressure range, a fuzzy-control of the compressor is stopped, and when the pressure detected by the high-pressure sensor is within the second target pressure range, a fuzzy-control of the compressor is performed. 
     
     
       8. The method according to  claim 1 , the air conditioner further includes:
 a pipe that connects an outdoor heat exchanger to an indoor heat exchanger; and 
 a super-cooling heat exchanger installed at the pipe. 
 
     
     
       9. The method according to  claim 8 , the air conditioner further includes:
 an inlet tube that extends from the super-cooling heat exchanger towards the receiver. 
 
     
     
       10. The method according to  claim 9 , the air conditioner further includes:
 a first valve installed at the inlet tube; and 
 a second valve installed at the outlet tube.